Today’s industries work 365 days round the clock. All systems are checked periodically to avoid the failures, as they could prove to be extremely costly. Non-destructive testing or NDT methods invariably carry out such checks so that there are no stoppages for accommodating these tests. This is true whether the industry in question is Nuclear or Aerospace and Power Generation or Pharmaceutical. Such NDT could utilize services such as Visual Testing, Radiography, Magnetic Testing, Eddy Current or Ultrasonic Testing.
Magnetic Testing utilizes different tools depending on the type of industry. Thus while the Pipeline Industry uses the Magnetic Flux Leakage (MFL) and the Portable Yoke, the Pulp & Paper Industry uses the Alternating Current Field Measurement Method or the ACFM. In the MFL method, which is used for the detection of pitting or corrosion in storage tanks, pipelines and other steel structures, a very powerful magnetic field is created for magnetizing the sample under test. The detector detects the gaps in the flux lines and analyzes them to assess the amount of missing metal as well as its dimensions. In an advanced version of this method, called the Magnetic Flux Leakage Inline Inspection Tool (MFL-ILI), the tool travels inside the pipeline and cleans the inner walls while detecting the corroded portions in the pipe wall. The ACFM method of magnetic testing can detect surface cracks as well as size them. The method applies to all metals and needs no direct contact, thereby making it possible to use it through coatings besides on surface temperatures up to 500 c.
Ultrasonic testing methods can not only detect flaws, cracks and corrosion in welded specimen such as piping, vessel and plate but it can also be used to measure the thickness of specimen. The professional equipment used could be Tank Crawlers, Near Drum Scanners, Internal Rotating Inspection Systems, Guided Ultrasonic Wave and Automated Pipe Scanners. Time Of Flight Diffraction (TOFD) method is used for both the Aerospace and Pulp & Paper Industries while the Aerospace and the Pipeline Industries use the Electromagnetic Acoustic Transmission (EMAT) method. The Petrochemical Industry uses Phased Array form of ultrasonic testing.
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